What Is a Feline Idiopathic Megacolon? Keeping your kittyโ€™s gut healthy.

What Is a Feline Idiopathic Megacolon? Photo by Ricardo Oliveira: https://www.pexels.com/photo/a-cat-lying-on-a-carpet-14189254/

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Feline idiopathic megacolon (FIM) is a syndrome that affects the large intestine and can cause constipation, vomiting, and abdominal distension.

Feline idiopathic megacolon is a condition that causes slower-than-normal movement within the large intestine. This can make defecation difficult for a cat with FIM, resulting in impacted feces or constipation. The condition is very rare, but it's important that you understand how it affects your cat and how to treat it. 

What is a Feline Idiopathic Megacolon?

Feline idiopathic megacolon (FIM) is a condition that causes the colon to become enlarged and inflamed. If a cat with FIM develops constipation, it can become difficult or impossible for them to pass feces, which then causes diarrhea. Symptoms of this long-term condition include abdominal pain, sometimes vomiting, and other signs such as weight loss or lethargy. While not contagious between cats, it can be passed from an infected mother cat to her kittens through her milk. 

What Causes Feline Idiopathic Megacolon?

Feline idiopathic megacolon is different from inflammatory bowel disease in cats, where the cat just has diarrhea. Feline idiopathic megacolon may have an unknown cause, or it may result from a problem with nerves controlling muscles of the colon (motor function). The syndrome appears to be inherited in some cats, while other cases occur sporadically or are acquired through an unknown cause.

In most cases, there is no known reason why your cat develops FIM. However, certain factors can make symptoms worse:

  • Activity level - Cats with low activity levels tend to have more severe constipation than those who exercise regularly. This is why Purina indoor cat food is advisable to prevent obesity and related conditions in your fluff.

  • Diet - Some diets contain higher amounts of fiber than others. If you feed your cat a diet higher in fiber than what naturally occurs in their prey animal diet (e.g., canned diets), that could lead to digestive problems such as FIM. 

How to Spot Signs of a Feline Idiopathic Megacolon?

If you suspect your cat has FIM, contact your veterinarian immediately so they can begin treatment as soon as possible. These are the common signs of FIM:

  • Increased appetite – This may well be due to your cat being fed equal portions of meals and treats. While snacks such as Temptations cat treats are well-balanced with nutrients, they need to be fed in moderation.

  • Diarrhea

  • Straining to defecate (often accompanied by crying)

  • Inability to defecate or pass stool, followed by abdominal discomfort and/or pain. The cat may be able to produce a small amount of hard stool, but nothing that he can pass. This also results in lethargy and dehydration. 

How Can I Treat My Cat's FIM?

Most of the time, FIM can be treated with special diets and pet medications. Your vet will also likely recommend a prescription diet such as Wellness cat food or Nulo cat food that helps lubricate your cat's digestive tract. The goal is to help move things through their system more easily so they'll go to the litter box more frequently and feel better overall.

Your vet may also advise you to ask your veterinarian about herbal treatments for constipation that you could try at home before bringing them in for treatment. Some of these include:

  • Dandelion root tea

  • Black walnut tincture (you can find this at any health food store)

  • The Honest Kitchen also offers a range of minimally-processed food with less fiber to suit the natural feline diet.

If none of these hacks works, your vet might have to do a surgical intervention in the form of subtotal colectomy

Risks and Complications Related to FIM

FIM affects cats of all ages, but it is most commonly seen in young to middle-aged cats. Males are more likely (around 70%) than females to have FIM.

Not surprisingly, there are risks and complications associated with FIM. The risk of developing a fecal impaction or obstruction is increased due to the large amount of feces that can accumulate in the colon (the last part of your cat’s digestive tract). Intestinal obstruction may lead to peritonitis, which is inflammation of the abdominal cavity lining caused by bacteria entering through an intestinal rupture or tear.

If left untreated, peritonitis can be fatal. Perforation means penetration through an organ wall. In this case, it refers to damage sustained by your cat's intestines due to constant pressure from retained stool along with prolonged dehydration that causes weakness in the walls of his intestines over time leading up until there's finally enough pressure against them that they burst open! 

Slower-Than-Normal Movement Within The Large Intestine

When a cat has FIM, the large intestine (colon) is not working as it should. The colon is responsible for moving food through your cat's digestive system. When FIM affects your cat's colon, it can make defecation difficult and painful for them. This can be very stressful for your kitty. Stomach worms could also be causing the problem and medications such as Panacur C might prove helpful. 


We’re glad that you’ve made it to the end of this article. Hopefully, we were able to give you a better understanding of what FIM is and how you can help your cat deal with it.

If you have any questions about our treatment recommendations or want more information on how we can help your cat, please reach out.

We look forward to hearing from you.

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